Semiconductor module including a switch and non-central diode

ABSTRACT

A semiconductor module having one or more silicon carbide diode elements mounted on a switching element is provided in which the temperature rise is reduced by properly disposing each of the diode elements on the switching element, to thereby provide a thermal dissipation path for the respective diode elements. The respective diode elements are arranged on a non-central portion of the switching element, to facilitate dissipation of the heat produced by each of the diode elements, whereby the temperature rise in the semiconductor module is reduced.

FIELD OF THE INVENTION

The present invention relates to semiconductor modules for use in powerconversion apparatuses such as inverters, and particularly to anarrangement of semiconductor elements inside the semiconductor modules.

BACKGROUND OF THE INVENTION

A semiconductor module for use in a power conversion apparatus such asan inverter includes a circuit, as shown in FIG. 13, formed by thecombination of a switching element such as an IGBT (insulated gatebipolar transistor) 101 and a diode element 102.

To satisfy the need in recent years for reducing the size of such asemiconductor module, a semiconductor module formed by providing a diodeelement on a switching element has been proposed in, for instance,Japanese Unexamined Patent Application Publication No. 2000-164800(paragraph 0019, FIG. 2).

However, when a diode element that includes silicon as a material(hereinafter called silicon diode element) is provided on a switchingelement that includes as a material conventionally and commonly usedsilicon (hereinafter called silicon switching element), both switchingelement and diode element need substantially the same electric currentdensity. For this reason, the silicon diode element becomes large enoughto substantially cover the whole of the silicon switching element, thusmaking it difficult to draw electric current out of the siliconswitching element.

To this end, another semiconductor module is proposed in which a diodeelement that includes, as a material, silicon carbide capable ofincreasing the electric current density and reducing the size of thediode element (hereinafter called silicon carbide diode element), isprovided on the silicon switching element.

For example, Japanese Unexamined Patent Application Publication No.2004-95670 (paragraph 0079, FIG. 6) discloses a semiconductor moduleformed by directly providing a silicon carbide diode chip in the middleportion of a silicon semiconductor element or chip, which portion is onthe emitter side of the element or chip.

Furthermore, Japanese Unexamined Patent Application Publication No.2003-243612 (paragraphs 0019, and 0029; FIG. 1) discloses another moduleformed by providing on a silicon semiconductor switching chip a wide gapsemiconductor, such as a the silicon carbide diode chip, having agreater energy band gap than that of silicon.

In the respective semiconductor modules as described above, an attemptto achieve a size reduction in semiconductor module is made by providinga silicon carbide diode element on a silicon switching element. However,the mere provision of the silicon carbide diode element on the siliconswitching element does not provide a good thermal dissipation path forthe silicon carbide diode element, thus causing heat produced by thediode element not to be dissipated but to be built up, which poses aproblem of excessive temperature rise in the semiconductor module. Theproblem becomes significant in the case of an increased electric currentdensity.

SUMMARY OF THE INVENTION

The present invention is directed to overcome the above-describedproblem with thermal dissipation from the above-described siliconcarbide diode element, and an object thereof is to provide asemiconductor module with a reduced temperature rise, by properlylocating the silicon carbide diode element on a silicon switchingelement to thereby provide a thermal dissipation path for the siliconcarbide diode element.

The feature of the present invention is that a semiconductor moduleincludes a switching element(s), and a silicon carbide diode element(s)provided in a non-central portion of the silicon switching element—i.e.,in a portion or at a position spaced away from the central portion ofthe switching element.

According to the present invention, a semiconductor module in which itstemperature rise is reduced can be provided through reduction of thetemperature rise due to heat produced by the silicon carbide diodeelement(s). These and other features, advantages and objects of thepresent invention will be further understood and appreciated by thoseskilled in the art by reference to the following drawings.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1 is a side view illustrating a semiconductor module according toEmbodiment 1 of the present invention;

FIG. 2 is a fragmentary top plan view illustrating the semiconductormodule according to Embodiment 1 of the present invention;

FIG. 3 is another fragmentary top plan view illustrating a semiconductormodule according to Embodiment 1 of the present invention;

FIG. 4 is a fragmentary top plan view illustrating a semiconductormodule according to Embodiment 2 of the present invention;

FIG. 5 is another fragmentary top plan view illustrating thesemiconductor module according to Embodiment 2 of the present invention;

FIG. 6 is a fragmentary top plan view illustrating a semiconductormodule according to Embodiment 3 of the present invention;

FIG. 7 is another fragmentary top plan view illustrating thesemiconductor module according to Embodiment 3 of the present invention;

FIG. 8 is a side view illustrating a semiconductor module according toEmbodiment 4 of the present invention;

FIG. 9 is a fragmentary top plan view illustrating another example of aconfiguration of a semiconductor module according to Embodiment 1 of thepresent invention;

FIG. 10 is a side view illustrating a semiconductor module according toEmbodiment 5 of the present invention;

FIG. 11 is a side view illustrating a semiconductor module according toEmbodiment 6 of the present invention;

FIG. 12 is a cross-sectional view illustrating a silicon carbide diodeelement using a p-silicon carbide substrate according to Embodiment 1through Embodiment 6; and

FIG. 13 is a diagram of a circuit including a diode element and an IGBTelement for use in the semiconductor module such as an inverter.

DESCRIPTION OF THE PREFERRED EMBODIMENTS Embodiment 1

FIG. 1 is a side view illustrating a semiconductor module according toEmbodiment 1 of the present invention.

On the surface of an insulation substrate 1 formed of aluminum nitrideor the like having high thermal conductivity and high electricalinsulation are provided a collector film 2 and an emitter film 3, madeof metal such as copper, while on the bottom surface thereof is provideda metal film 4 made of copper or the like.

A silicon IGBT element 5 serving as a silicon switching element isprovided on the collector film 2, and both element 5 and film 2 arejoined together by solder. In the present case, the collector of thesilicon IGBT element 5 is jointed joined with the collector film 2. Thisestablishes an electrical connection between the collector of thesilicon IGBT element 5 and the collector film 2.

Furthermore, an insulation film 6 formed of aluminum nitride or the likehaving high thermal conductivity and high electrical insulation isprovided on the emitter of the silicon IGBT element 5, and is joined bysolder to the emitter of the element 5. In the present case, theinsulation film 6 is provided on the non-central portion of the siliconIGBT element 5.

Moreover, on the insulation film is provided a cathode film 7 made ofmetal such as copper.

Also, a silicon carbide diode element 8 is provided on the cathode film7, and is joined by solder with the film 7. This establishes anelectrical connection between the cathode of the silicon carbide diodeelement 8 and the cathode film 7. Here, preferably, a silicon carbideSchottky barrier diode (SiC-SBD) is used for the silicon carbide diodeelement 8.

In addition, a base substrate 9 made of metal such as copper is providedon the metal film 4 opposite the insulation substrate 1, and is joinedby solder with the metal film 4. The base substrate 9 and the insulationsubstrate 1 act as a heat dissipater that dissipates heat from thesemiconductor elements.

Further, there are provided a first wire 10, a second wire 11 and athird wire 12 each serving as a current input output portion—i.e., aconductor through which electric current flows into or from the siliconIGBT element 5 and the silicon carbide diode element 8. One end of thefirst wire 10 is joined with an anode of the silicon carbide diodeelement 8 and the other end thereof, with the emitter film 3. One end ofthe second wire 11 is joined with an emitter of the silicon IGBT element5 and the other end thereof, with the emitter film 3. One end of thethird wire 12 is joined with a cathode film and the other end thereof,with the collector film 2. Here, the first wire 10, the second wire 11and the third wire 12 each includes, as a material, metal such asaluminum (Al) and gold (Au).

FIGS. 2 and 3 are fragmentary top plan views of the semiconductor moduleaccording to Embodiment 1 of the present invention, each illustrating adetailed arrangement of the insulation film 6, cathode film 7 andsilicon carbide diode element 8 with respect to the silicon IGBT element5.

The insulation film 6, the cathode film 7 and the silicon carbide diodeelement 8 are provided in such a manner that the silicon carbide diodeelement 8 is placed on the non-central portion of the silicon IGBTelement 5, as is shown in FIGS. 2 and 3.

In this way, in the semiconductor module according to Embodiment 1,placing the silicon carbide diode element 8 on the non-central portionof the silicon IGBT element 5 facilitates heat dissipation from thesilicon diode element 8. Consequently, a temperature rise due to heatproduced by the silicon carbide diode element 8 can be reduced, which inturn reduces the temperature rise in the semiconductor module.

Here, FIGS. 2 and 3 each depict the silicon IGBT element 5 in the caseof rectangular-shaped one that is typically used.

In this manner, when the silicon IGBT element 5 is rectangular-shaped,the silicon diode element 8 is disposed, as shown in FIG. 2, in closeproximity to a side of the non-central portion of the rectangular shapedsilicon IGBT element 5, whereby heat dissipation from the siliconcarbide diode element 8 is facilitated in the direction indicated byarrow A. Thus, the temperature rise in the silicon carbide diode element8 can be reduced, which, in turn, results in reduction in thetemperature rise in the semiconductor module.

Alternatively, provision of the silicon carbide diode element 8, asshown in FIG. 3, on a corner of the rectangular-shaped silicon IGBTelement 5 facilitates heat dissipation from the silicon diode element 8along the directions indicated by arrows B and C. Thus, this arrangementenables the temperature rise in the silicon carbide diode element 8 tobe reduced further than by positioning the diode element 8 in closeproximity to a side of the rectangular-shaped silicon IGBT element 5,which results in further reduction in the temperature rise in thesemiconductor module.

In Embodiment 1, a single silicon carbide diode element 8 is located onthe non-central portion of the silicon IGBT element 5; further, a methodof enhancing heat dissipation from the silicon carbide diode element isto dispose a plurality of silicon carbide diode elements on thenon-central portion of the silicon IGBT element 5, whereby thetemperature rise in the silicon carbide diode element can be reducedfurther than that shown in Embodiment 1. A case of using a plurality ofsilicon carbide diode element will be described below.

Embodiment 2

Embodiment 2 according to the present invention, where a plurality ofsilicon diode elements are used, is such that two silicon carbide diodeelements are disposed on a non-central portion of the silicon IGBTelement 5.

FIGS. 4 and 5 are fragmentary views of top plans of a semiconductormodule according to Embodiment 2 of the present invention, each showingdetailed arrangements of insulation films 13 a, 13 b, cathode films 14a, 14 b, and silicon carbide diode elements 15 a, 15 b, on the siliconIGBT element 5. As is shown in FIGS. 4 and 5, the insulation films 13 a,13 b, the cathode films 14 a, 14 b and the silicon carbide diodeelements 15 a, 15 b are provided in such a manner that the diodeelements 15 a, 15 b are positioned on the non-central portion of theIGBT element 5.

FIG. 1 illustrating Embodiment 1 can be used as the side view of themodule according to Embodiment 2. The configuration of the semiconductormodule according to Embodiment 2 corresponds to a configuration where,in FIG. 1, the insulation film 6 is replaced with the insulation films13 a, 13 b; the cathode film 7, with the cathode films 14 a, 14 b; andthe silicon carbide diode element 8, with the silicon carbide diodeelements 15 a, 15 b.

Describing in greater detail the configuration, the insulation films 13a, 13 b, made of aluminum nitride, are provided on the emitter of thesilicon IGBT element 5 and joined by solder with the emitter thereof,and in the present case, the films 13 a, 13 b are provided on thenon-central portion of the element 5.

Next, on the insulation films 13 a, 13 b are provided the cathode film14 a, 14 b, each made of metal such as copper.

Finally, the silicon carbide diode element 15 a is provided on thecathode film 14 a and joined by solder with the film 14 a; the siliconcarbide diode element 15 b is provided on the cathode film 14 b andjoined by solder with the film 14 b. In the present case, the cathodesof the silicon carbide diode elements 15 a, 15 b are joined with thecorresponding cathode films. This causes the cathodes of the diodeelement 15 a, 15 b to electrically connect to the cathode films 14 a, 14b, respectively. Here, preferably, the silicon carbide Schottky barrierdiode is utilized as the silicon carbide diode element 15 a, 15 b.

In addition, although not illustrated herein, the semiconductor modulein Embodiment 2 uses as the input output portion (conductor) the firstwire 10, the second wire 11 and the third wire 12. One end of each firstwire 10 is joined with an anode of each of the silicon carbide diodeelements 15 a, 15 b and the other end thereof, with the emitter film 3.One end of the second wire 11 is joined with an emitter of the siliconIGBT element 5 and the other end thereof, with the emitter film 3. Oneend of each third wire 12 is joined with each of the cathode films 14 a,14 b and the other end thereof, with the collector film 2.

Because configurations of other elements correspond to those in FIG. 1illustrating Embodiment 1, they will not be provided herein.

In this way, with the semiconductor module according to Embodiment 2,where a plurality of the diode elements is used, positioning the twosilicon carbide diode elements 15 a, 15 b on the non-central portion ofthe silicon IGBT element 5 facilitates heat dissipation from the silicondiode element 8. In addition, the use of two silicon carbide diodeelements allows electric current density borne by a single siliconcarbide diode element to lower, thus reducing the volume of heatproduced by the single diode element. Consequently, the temperature risedue to heat produced by the silicon carbide diode element can be reducedfurther than by using one silicon carbide diode element. This embodimentcan further reduce the temperature rise in the semiconductor module incomparison with Embodiment 1.

Here, FIGS. 4 and 5 illustrate the silicon IGBT element 5 that iscommonly used rectangular-shaped one.

In this way, when the silicon IGBT element 5 is rectangular-shaped, thesilicon diode elements 15 a, 15 b are disposed, as shown in FIG. 4, inclose proximity to two sides of the non-central portion of therectangular shaped silicon IGBT element 5, whereby heat dissipation ofthe silicon carbide diode elements 15 a, 15 b is facilitated along thedirections indicated by arrows D, E in FIG. 4. In addition, the use oftwo silicon carbide diode elements permits reduction of the electriccurrent density borne by a single silicon carbide diode element. Hence,the temperature rise in the silicon carbide diode elements 15 a, 15 b isreduced further than by using a single silicon carbide diode element. Inthe present case, the temperature rise in the module can be reducedfurther than that shown in Embodiment 1.

Further, as shown in FIG. 5, the provision of the silicon carbide diodeelements 15 a, 15 b on a corner (non-central portion) of therectangular-shaped silicon IGBT element 5 facilitates, along thedirections indicated by arrows F, G, H and I, the heat dissipation fromthe silicon diode elements 15 a, 15 b. Thus, this arrangement enablesthe temperature rise in the silicon carbide diode elements 15 a, 15 b tobe reduced further than by positioning the diode element 8 in closeproximity to two sides of the rectangular-shaped silicon IGBT element 5,which results in further reduction in the temperature rise in thesemiconductor module.

Embodiment 3

In Embodiment 2 according to the present invention in which a pluralityof silicon diode elements are used, it is shown that two silicon carbidediode elements 15 a, 15 b are disposed on a non-central portion of thesilicon IGBT element 5. In Embodiment 3, four silicon carbide diodeelements are arranged on the non-central portion thereof.

FIGS. 6 and 7 are fragmentary views of top plans illustrating asemiconductor module according to Embodiment 3 of the present invention,each depicting an detailed arrangement of the insulation films 16 a-16d, the cathode films 17 a-17 d and the silicon carbide diode elements 18a-18 d, on the silicon IGBT element 5. The insulation films 16 a-16 d,the cathode films 17 a-17 d and the silicon carbide diode elements 18a-18 d are provided in such a manner that the diode elements 18 a-18 dare placed on the non-central portion of the silicon IGBT element 5, asis shown in FIGS. 6 and 7.

FIG. 1 illustrating Embodiment 1 can be used as the side view of themodule according to Embodiment 3. The configuration of the semiconductormodule according to Embodiment 3 corresponds to a configuration where,in FIG. 1, the insulation film 6 is replaced with the insulation films16 a-16 d; the cathode film 7, with the cathode films 17 a-17 d; and thesilicon carbide diode element 8, with the silicon carbide diode elements18 a-18 d.

Describing in greater detail the configuration, the insulation films 16a-16 d made of aluminum nitride are provided on the emitter of thesilicon IGBT element 5, and are joined by solder with the emitterthereof, and in the present case the insulation films 16 a-16 d areprovided on the non-central portion of the element 5.

Further, on the insulation films 16 a-16 d are provided the cathodefilms 17 a-17 d each made of metal such as copper.

The silicon carbide diode element 18 a-18 d are provided on the cathodefilms 17 a-17 d, respectively and are joined by solder with therespective films 17 a-17 d. In the present case, the cathodes of thesilicon carbide diode elements 18 a-18 d are jointed with thecorresponding cathode films. This establishes electrical connectionsbetween the cathodes of the silicon carbide diode elements 18 a-18 d andthe corresponding cathode films 17 a-17 d. Here, preferably, the siliconcarbide Schottky barrier diode is utilized as the silicon carbide diodeelement 18 a, 18 b.

In addition, although not illustrated herein, the semiconductor modulein Embodiment 3 uses as the input output portion (conductor) the firstwire 10, the second wire 11 and the third wire 12. One end of each ofthe first wires 10 is joined with an anode of each of the siliconcarbide diode elements 18 a-18 d and the other end of each thereof, withthe emitter film 3. One end of the second wire 11 is joined with anemitter of the silicon IGBT element 5 and the other end thereof, withthe emitter film 3. One end of each of the third wires 12 is joined witheach of the cathode films 17 a-17 d and the other end of each thereof,with the collector film 2.

Because configurations of other elements correspond to those shown inFIG. 1 in Embodiment 1, they will not be provided herein.

In this way, in the semiconductor module according to Embodiment 3 wherea plurality of the diode elements are used, placement of the foursilicon carbide diode elements 18 a-18 d on the non-central portion ofthe silicon IGBT element 5 facilitates heat dissipation from the siliconcarbide diode elements 18 a-18 d. In addition, the use of four siliconcarbide diode elements allows electric current density borne by a singlesilicon carbide diode element to lower, thus reducing the volume of heatproduced by the single diode element. Consequently, the temperature risedue to heat produced by the silicon carbide diode element can be reducedfurther than by using two silicon carbide diode elements. In the presentcase, the temperature rise in the semiconductor module can be reducedfurther than that shown in Embodiment 2.

Here, FIGS. 6 and 7 illustrate the silicon IGBT element 5 that iscommonly used rectangular-shaped one.

In this way, when the silicon IGBT element 5 is rectangular-shaped, thesilicon diode elements 18 a-18 d are disposed, as shown in FIG. 6, inclose proximity to four sides of the non-central portion of therectangular shaped silicon IGBT element 5, whereby the heat dissipationfrom the silicon carbide diode elements 18 a-18 d is facilitated alongthe directions indicated by arrows J, K, L and M in FIG. 6. In addition,the use of four silicon carbide diode elements allows electric currentdensity borne by a single silicon carbide diode element to lower. Hence,the temperature rise in the silicon carbide diode elements 18 a-18 d isreduced further than by using two silicon carbide diode elements. In thepresent case, the temperature rise in the module can be reduced furtherthan that shown in Embodiment 2.

Further, as shown in FIG. 7, the silicon carbide diode elements 18 a-18d are located on the four corners (non-central portion) of therectangular shaped silicon IGBT element 5, whereby heat dissipation fromthe silicon carbide diode elements 18 a-18 d is facilitated along thedirections indicated by arrows N, P, Q, R, S, T, U and V in FIG. 7. Forthis reason, the temperature rise in the silicon carbide diode elementcan be reduced further than by disposing the silicon diode elements 18a-18 d in close proximity to the four sides of the rectangular shapedsilicon IGBT element 5. As a result, the temperature rise in the modulecan be further reduced.

Embodiment 4

In Embodiment 1, it is shown that the first wire 10, the second wire 11and the third wire 12 are employed as the input output portion(conductor) through which electric current flows into or from thesilicon IGBT element 5 and the silicon carbide diode element 8. InEmbodiment 4 of the present invention, the first wire 10, the secondwire 11 and the third wire 12 are replaced with a first lead strip 21, asecond lead strip 22 and a third lead strip 23 each made of metal suchas copper. Because configurations of other elements correspond to thoseshown in FIG. 1 in Embodiment 1, they will not be provided herein.

In this way, in the semiconductor module according to Embodiment 4, theuse of the first lead strip 21, the second lead strip 22 and the thirdlead strip 23 facilitates heat dissipation from the semiconductorelements by way of the lead strips. In particular, since the first leadstrip 21 and the third lead strip 23 contribute to heat dissipation fromthe silicon carbide diode element 8 whose temperature tends to rise, thetemperature rise in the diode element 8 can be reduced. Further, becausethe second lead strip 22 contributes to heat dissipation from thesilicon IGBT element 5, the temperature rise in the IGBT element 5 canbe reduced. In the present case, the temperature rise in thesemiconductor modules can be reduced further than that shown inEmbodiment 1.

Further, the first lead strip 21, the second lead strip 22 and the thirdlead strip 23, as described in the present embodiment, is applicable toEmbodiment 2 as well. In that case, the semiconductor module uses as theinput output portion (conductor) the first lead strip 21, the lead strip22 and the third lead strip 23. One end of each of the first lead strips21 is joined with an anode of each of the silicon carbide diode elements15 a, 15 b and the other end of each thereof, with the emitter film 3.One end of the second lead strip 22 is joined with an emitter of thesilicon IGBT element 5 and the other end thereof, with the emitter film3. One end of each of the third lead strips 23 is joined with each ofthe cathode films 14 a, 14 b and the other end of each thereof, with thecollector film 2.

With this arrangement, the temperature rise due to heat produced by thesilicon carbide diode elements 15 a, 15 b whose temperature particularlytends to rise, can be reduced. In the present case, the temperature risein the semiconductor modules can be reduced further than that shown inEmbodiment 2.

Further, the first lead strip 21, the second lead strip 22 and the thirdlead strip 23, as described in the present embodiment, are applicable toEmbodiment 3 as well. In that case, the semiconductor module uses as theinput output portion (conductor) the first lead strip 21, the lead strip22 and the third lead strip 23. One end of each of the first lead strips21 is joined with an anode of each of the silicon carbide diode elements18 a-18 d and the other end of each thereof, with the emitter film 3.One end of the second lead strip 22 is joined with an emitter of thesilicon IGBT element 5 and the other end thereof, with the emitter film3. One end of each of the third lead strips 23 is joined with each ofthe cathode films 17 a-17 d of the corresponding silicon carbide diodeelements 18 a-18 d and the other end of each thereof, with the collectorfilm 2.

This arrangement enables reduction in the temperature rise due to heatproduced by the silicon carbide diode elements 18 a, 18 b whosetemperature particularly tends to rise. In the present case, thetemperature rise in the semiconductor elements can be reduced furtherthan that shown in Embodiment 3.

In Embodiment 1 through Embodiment 4, since the temperature rise due toheat produced by the silicon carbide diode elements 8, 15 a, 15 b and 18a-18 d, is reduced, the material for the insulation films 6, 13 a, 13 band 16 a-16 d can be changed from aluminum nitride to less-expensiveepoxy resin. This change allows for reduction in manufacture/fabricationcost of the semiconductor module.

In Embodiment 1 through Embodiment 4, it is shown that the siliconcarbide diode elements 8, 15 a, 15 b and 18 a-18 d are arranged on thenon-central portion of the silicon IGBT element 5, and corresponding tothis arrangement, the insulation films 6, 13 a, 13 b and 16 a-16 d, andthe cathode film 7, 14 a, 14 b and 17 a-17 d are also arranged on thenon-central portion thereof. The insulation films and the cathode films,however, do not need to be split. For instance, the insulation film 6and the cathode film 7, as shown in FIG. 1 illustrating Embodiment 1,may be provided on the entire surface of the emitter of the silicon IGBTelement 5, with the silicon carbide diode elements 8, 15 a, 15 b and 18a-18 d each being provided on a portion of the cathode film 7 located inthe non-central portion of the IGBT element 5.

FIG. 9 is a fragmentary top plan view showing an example of providingthe insulation film 6, and the cathode film 7 on the entire surface ofthe emitter of the silicon IGBT element 5, based on FIG. 2 illustratingEmbodiment 1. As shown in FIG. 9, the insulation film 6 is provided onsubstantially the entire surface of the emitter of the silicon IGBTelement 5, and also the cathode film 7 on substantially the entiresurface of the insulation film 6. The silicon carbide diode element 8 isjoined with a portion of the cathode film 7 corresponding to thenon-central portion of the silicon IGBT element 5. In this situation,each of the insulation film 6 and the cathode 7 needs to partially beremoved at a place where the wire or the lead strip is to be joined, andalso at a place for the gate. It should be understood, as a matter ofcourse, that the description illustrating FIG. 9 is applicable toEmbodiment 2 through Embodiment 4.

Embodiment 5

FIG. 10 is a side view illustrating a semiconductor module according toEmbodiment 5 of the present invention. The difference between FIG. 1illustrating Embodiment 1 and FIG. 10 is that the anode of the siliconcarbide diode element 8 is directly joined by solder or the like withthe emitter of the silicon IGBT element 5. In the present case, thesilicon carbide diode element 8 is placed upside down in comparison withthat in FIG. 1 illustrating Embodiment 1. This arrangement causes theemitter of the IGBT element 5 to electrically connect with the anode ofthe diode element 8. Here, the same reference numerals refer to likeelements in FIG. 1 (illustrating Embodiment 1) and FIG. 10, and nodescription of the corresponding elements will be provided herein.

This arrangement also eliminates the need for the insulation film 6,thus facilitating heat dissipation of the diode element 8 toward theIGBT element 5. Consequently, the temperature rise due to heat producedby the silicon carbide diode element 8 can be reduced further than byusing the insulation film 6. In the present case, the temperature risein the semiconductor module can be reduced further than that shown inEmbodiment 1.

The insulation film 6 and the first wire 10 can be eliminated, thusreducing manufacture/fabrication cost for the semiconductor module.Further, the elimination of the first wire 10 provides an advantage ofpermitting a simplification in internal wiring of the module.

Here, the configuration, as shown in Embodiment 5, in which the anode ofthe diode element 8 is directly joined with the emitter of the IGBTelement 5, can be made corresponding to that in Embodiment 2 in which aplurality of the diode elements is employed. In that case, the anodes ofthe diode elements 15 a, 15 b are directly joined with the emitter ofthe IGBT element 5.

This allows the temperature rise due to heat produced by the diodeelements 15 a, 15 b to be reduced. In that case, the temperature rise inthe semiconductor module can be reduced further than that shown inEmbodiment 2.

Further, the configuration, as shown in Embodiment 5, in which the anodeof the diode element 8 is directly joined with the emitter of the IGBTelement 5, can be made corresponding to that in Embodiment 3 in which aplurality of the diode elements is used. In that case, the anodes of thesilicon carbide diode elements 18 a-18 d are directly joined with theemitter of the silicon IGBT element 5.

This allows for reduction in the temperature rise due to heat producedby the silicon carbide diode elements 18 a-18 d. In that case, thetemperature rise in the semiconductor module can be reduced further thanthat shown in Embodiment 3.

Embodiment 6

FIG. 11 is a side view illustrating a semiconductor module according toEmbodiment 6 of the present invention. The difference between FIG. 10illustrating Embodiment 5 and FIG. 11 is that in place of the secondwire 11 and the third wire 12, the second lead strip 22 serving as thecurrent input output portion—i.e., a conductor through which electriccurrent flows into or from the corresponding element—is used to connectthe emitter of the silicon IGBT element 5 with the emitter film 3, andthe third lead strip 23 serving as the current input output portion(conductor) is used to connect the cathode of the silicon carbide diodeelement 8 with the collector film 2. Here, the same reference numeralsrefer to like elements in FIG. 10 (illustrating Embodiment 5) and FIG.11, and no description of the corresponding elements will be providedherein.

This arrangement eliminates, as is the case with Embodiment 5, theinsulation film 6, which thus facilitates heat dissipation from thesilicon carbide diode element 8 in the direction toward the silicon IGBTelement 5 as well. In addition, the use of the second and third leadstrips 22, 23 provides better heat dissipation for the module. Sinceespecially the lead strip 23 contributes to heat dissipation of thesilicon carbide diode element 8 whose temperature is prone to rise, thetemperature rise in the diode element 8 can be reduced, while the leadstrip 22 contributes to heat dissipation of the silicon IGB element 5,the temperature rise in the IGBT element 5 can be reduced. In thepresent case, the temperature rise can be reduced further than thatshown in Embodiment 5.

Moreover, elimination of the insulation film 6 and the first lead strip21 allows for reduction in manufacture/fabrication cost of thesemiconductor module. Further, the first lead strip 21 may beeliminated, thus providing an advantage in making internal wiring of thesemiconductor module simple.

Further, the configuration shown in Embodiment 6—in which the anode ofthe silicon carbide diode element 8 is directly joined with the emitterof the silicon IGBT element 5, and also the second lead strip 22 and thethird lead strip 23 are used—can be made corresponding to Embodiment 3in which a plurality of silicon carbide diode elements is employed. Inthat case, the anodes of the silicon carbide diode element 15 a, 15 bare directly joined with the emitter of the silicon IGBT element 5.Further, one end of the second lead strip 22 is joined with the emitterof the silicon IGBT element 5 and the other end thereof, with theemitter film 3, while one end of the second lead strip 23 is joined withthe cathode of the silicon carbide diode elements 15 a, 15 b, and theother end thereof, with the emitter film 2.

This arrangement allows for reduction in the temperature rise due toheat produced by the silicon carbide diode elements 15 a, 15 b whosetemperature is particularly prone to rise. In that case, the temperaturerise in the semiconductor module can be reduced further than that shownin Embodiment 5.

Further, the configuration shown in Embodiment 6—in which the anode ofthe silicon carbide diode element 8 is directly joined with the emitterof the silicon IGBT element 5, and also the second lead strip 22 and thethird lead strip 23 are used—can be made corresponding to Embodiment 4in which a plurality of silicon carbide diode elements is employed. Inthe present case, the anodes of the silicon carbide diode element 18a-18 d are directly joined with the emitter of the silicon IGBT element5. Further, one end of the second lead strip 22 is joined with theemitter of the silicon IGBT element 5 and the other end thereof, withthe emitter film 3, while one end of the second lead strip 23 is joinedwith the cathode of the silicon carbide diode elements 18 a-18 d and theother end thereof, with the emitter film 2.

This arrangement permits reduction in the temperature rise due to heatproduced by the silicon carbide diode elements 18 a-18 d whosetemperature is particularly prone to rise. In that case, the temperaturerise in the semiconductor module can be reduced further than that shownin Embodiment 5.

Throughout all of the embodiments, the silicon carbide diode elementfabricated using any one of an n-silicon carbide substrate or ap-silicon carbide substrate, may be employed. For Embodiment 5 andEmbodiment 6, it is preferable to use the silicon carbide diode elementfabricated by using the p-silicon carbide substrate on which entiresurface an anode can be formed, as shown in FIG. 11. FIG. 12 shows anexample of the silicon carbide diode element using such a p-siliconcarbide substrate. In FIG. 12 are shown a p-silicon carbide substrate31, an n-diffusion layer 32 formed within the surface of the p-siliconcarbide substrate 31, a cathode 33 formed on the surface of thep-silicon carbide substrate 31, a protection film 34 formed on thesurface of the p-silicon carbide substrate 31, including an area of itsn-diffusion layer 32 located in the periphery of the cathode 33, and ananode 35 formed on the rear surface of the p-silicon carbide substrate31.

While it is shown that all the embodiments use the IGBT element as theswitching element, another type of the switching element such as, forinstance, an MOSFET (metal oxide semiconductor field effect transistor)element, or a bipolar transistor element can be employed, which iswithin the scope of the invention.

In addition, the advantage attained by the present invention can beachieved by replacing the silicon switching element with the siliconcarbide switching element using silicon carbide as a material. It shouldbe appreciated that the scope of the present invention includes the useof the silicon switching element. While the present invention has beenshown and described with reference to preferred embodiments thereof, itwill be understood by those skilled in the art that variousmodifications and the like could be made thereto without departing fromthe spirit and scope of the invention.

1. A semiconductor module, comprising: a switching element including atop surface and a bottom surface opposing the top surface; and a siliconcarbide diode element provided on a non-central portion of the topsurface of the switching element, a bottom surface of the siliconcarbide diode element facing the top surface of the switching elementand being electrically insulated from the top surface of the switchingelement, wherein the switching element is rectangular-shaped and thesilicon carbide diode element is provided on the top surface of theswitching element in close proximity to a corner of the switchingelement.
 2. The semiconductor module of claim 1, wherein an input outputportion, through which electric current flows into or from the switchingelement and the silicon carbide diode element, is made of a lead strip.3. The semiconductor module of claim 1, further comprising: aninsulation film between the switching element and the silicon carbidediode element, the insulation film being made of epoxy resin.
 4. Thesemiconductor module of claim 1, wherein the switching element is anyone of a silicon IGBT element, a silicon carbide IGBT element, a siliconMOSFET element and a silicon carbide MOSFET element.
 5. A semiconductormodule, comprising: a switching element including a top surface and abottom surface opposing the top surface; and a plurality of siliconcarbide diode elements provided on a non-central portion of the topsurface of the switching element, a bottom surface of each of theplurality of silicon carbide diode elements facing the top surface ofthe switching element, wherein the switching element isrectangular-shaped and each of the plurality of silicon carbide diodeelements is provided on a top surface of the switching element in closeproximity to a corner of the switching element.
 6. The semiconductormodule of claim 5, wherein a number of the plurality of silicon carbidediode elements is between two to four.
 7. The semiconductor module ofclaim 5, wherein an input output portion, through which electric currentflows into or from the switching element and each of the plurality ofthe silicon carbide diode elements, is made of a lead strip.
 8. Thesemiconductor module of claim 5, further comprising: an insulation filmbetween the switching element and each of the plurality of siliconcarbide diode elements, the insulation film being made of epoxy resin.9. The semiconductor module of claim 5, wherein the switching element isany one of a silicon IGBT element, a silicon carbide IGBT element, asilicon MOSFET element and a silicon carbide MOSFET element.